This invention relates to a waveguide-type optical sensor for optically sensing voltage, temperature, pressure, humidity and other phystical quantities.
Optical transmissions are highly advantageous in that they are not influenced by electromagnetic noise. For this reason, light is suitable as the medium for transmitting data in an environment where much electromagnetic noise is encountered. The use of optical fibers enables optical data transmission with little loss and therefore allows data to be transmitted over comparatively long distances. If the data for optical transmission are measurement data, such as measured values indicative of certain physical quantities, it is preferred that measurement or detection be performed in the form of light, i.e., in an optic mode, and that the resulting measurement data be transmitted optically as such through an optical fiber. A very practical device for accomplishing this is referred to as an optical sensor or optical fiber sensor.
In order to measure such physical quantities as voltage, pressure, temperature and humidity with a high degree precision and over a wide dynamic range, it is required that use be made of a plurality of sensing elements having sensitivities and sensing regions that differ from one another. If optical fibers of a number equal to that of these plural sensing elements are provided in order to optically transmit the measurement data obtained from the respective elements, a large quantity of these optical fibers will be necessary. If the data are to be optically transmitted over long distances, procuring the optical fibers will entail considerable expense.
Likewise, if voltage, pressure, temperature, humidity and other physical quantities are to be measured simultaneously, a plurality of sensing elements of a type which will depend upon the kinds of physical quantities measured will be required. As mentioned above, providing optical fibers for respective ones of these plural elements to optically transmit the measurement data obtained from them demands a large number of optical fibers and, hence, results in considerable expenditure for long-distance optical transmission.
Thus, a problem encountered in the prior art is high cost which results from the need to provide an optical fiber for each sensing element in order to optically transmit data from the element.